This invention relates to methods of and a kit used in testing human male semen for potential fertility. More particularly, this invention relates to methods of and a kit for testing human male fertility by in vitro testing of sperm metabolism in a semen sample.
Generally, tests which provide an assessment of the potential fertility of sperm are ordered through a physician. This can be a relatively expensive procedure since one must visit the physician's office and pay the physician's fee as well as lab fees. If a man is undergoing treatment for infertility, repeated trips to physician's office for testing adds expense as well as inconvenience to the procedure. In addition, there are individuals who are hesitant to seek treatment from a physician because they have no objective basis for requesting treatment. If an individual, in the privacy of his home, can at least preliminarily assess objectively the potential fertility of his sperm, many of the shortcomings associated with current test methods can be avoided. While providing for self-testing is important, it is also useful to provide a more convenient approach for laboratory testing of sperm samples wherein the tests can be conducted utilizing relatively inexpensive, readily available equipment.
In conventional sperm analysis, in which sperm count and sperm motility are the primary factors, there are no strict threshold levels separating fertility from infertility, except in the situation wherein there are no moving sperm, which is always associated with infertility. A sperm count of twenty million sperm per milliliter or greater is generally considered to be in the fertile range, whereas a lower count is considered subfertile. There is some disagreement on this in that some laboratories and clinicians use rates of thirty million sperm per milliliter or forty million sperm per milliliter as the fertility threshold. These values are not fixed in that it has been determined that twenty percent of human males with counts below twenty million sperm per milliliter will father children and as many as fifteen percent of human males with normal sperm counts may have some degree of sperm dysfunction due to other reasons which interfere with fertility. A sperm specimen with normal sperm count or with normal sperm motility does not invariably establish fertility in that individual. In addition, there is disagreement as to what constitutes the lower limit of sperm motility that can be considered normal or fertile, with estimates ranging between forty to sixty percent of the sperm in a given sample. In summary, sperm analysis is not one hundred percent accurate and in characterizing human male patients as fertile or infertile, the accuracy of the characterization is generally less than ninety percent.
It has been found that a measurement of human male fertility is the collective metabolism rate of the sperm in an ejaculate. Such a measurement takes into consideration both sperm count and sperm motility, which provides a basis for calculating the proportion of the total sperm population theoretically capable of fertilizing the ovum.
While resazurin, as well as methylene blue, have been used to test the potential fertility of bovine semen samples, there has been no indication that resazurin could be used effectively in testing semen samples of human males for potential fertility because generally, bull semen has much higher sperm densities than human semen, e.g., on the order of one billion sperm per milliliter for a fertile bull, in contrast to 70 to 100 million sperm per milliliter for a fertile human male. Also, the research on bull semen tested the rate at which the dye became pink or colorless, a technique not readily adaptable to use in a kit intended primarily for home testing, and most, if not all, of the bull ejaculates were fertile and the objective of the testing was to measure the degree of fertility rather than attempting to distinguish between fertile and sub-fertile or infertile ejaculates. The use of resazurin for bovine semen analysis is set forth in R. E. Erb et al., "Resazurin Reducing Time as an Indicator of Bovine Semen Fertility Capacity", Journal of Dairy Science. page 853, December 1950 and R. E. Erb et al., "Modified Resazurin Reduction Test for Estimating Fertility Capacity of Bull Semen", Journal of Dairy Science, page 881, 1952. The utilization of resazurin for testing bull semen has its origins in the use of resazurin as a reagent in testing milk.